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Posted to users@groovy.apache.org by "Winnebeck, Jason" <Ja...@windstream.com> on 2015/11/06 22:42:29 UTC
Command Chain in assert
Is it possible to support command chain in asserts? I'm trying to create a testing DSL.
The expression item("abc").exists will return a boolean. So I can do this:
item "abc" exists
But I can't do this:
assert item "abc" exists
Is something like that possible?
Jason
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RE: Command Chain in assert
Posted by "Winnebeck, Jason" <Ja...@windstream.com>.
OK, thanks for insight into the problem. The idea from https://issues.apache.org/jira/browse/GROOVY-4808 to allow command chains in parens is a good one though, in all cases discussed so far it is a possible solution, and it doesn't preclude Groovy from implementing smarter logic in the future when parens are not present if a reasonable, unambiguous solution is discovered. For the problem you described about multiple interpretation of foo x == bar y, that sounds more like an operator precedence problem. I realize command chains are not exactly "operators," but in my mind I think of it in the same way -- does chaining take precedence over a binary operator or not? It seems reasonable that some choice can be made there, and if you want a different choice, you use parens just like any other case, and some can consider parens to be required to be good style as in the case of (A && B || C) -- the compiler says && comes before || but as a developer I am always forgetting if && comes before || so as a matter of style I always use parens -- either (A && B) || C or A && (B||C). I think the same argument could apply to operators within command chains -- pick one way and require parens for the other.
Jason
-----Original Message-----
From: Jochen Theodorou [mailto:blackdrag@gmx.org]
Sent: Monday, November 09, 2015 9:05 AM
To: users@groovy.incubator.apache.org
Subject: Re: Command Chain in assert
On 09.11.2015 14:29, Winnebeck, Jason wrote:
> That ticket was useful. Just out of curiosity, is there a way to make
> the DSL work if I do provide a function assert? I’m not sure it could,
> because you’d need to support operators, and also when I tried to make
> such a DSL I was not able to actually declare any symbol assert and be
> able to call it how I’d expect. Even if it worked you’d lose power
> assert. I wonder (not that I think it would be worth it) if it’s even
> possible to implement with an AST? I’m thinking even that is not
> possible because Groovy can’t even parse the syntax so you’d never get
> to AST stage.
transforms still require that the program can be parsed... so no, it would not work with them
as for the problem itself... let me try making an example...
assert foo x == bar y
you interpret that as
assert foo(x) == bar(y)
but the compiler can interpret that as
assert foo(x==bar).y
In short the grammar cannot easily know which of those two is the right thing, especially since both variants are valid.
We actually had maybe a similar problem with handling of = in asserts.
As you may know doing something like "assert x=1" will not be accepted by the compiler. To solve this we basically changed the rule in the grammar from
"assert" expression
to
"assert" assignmentLessExpression
with the later one being a sub rule that contains any expression minus assignment. So to solve the issue in a similar way we would need something like this:
"assert" assignmentAndEqualsLessExpression ( "==" expression)?
where assignmentAndEqualsLessExpression does, in a similar matter, no allow for expressions with directly a == in it.
And now the big trouble.... the command chain rules are not of that kind. They allow "==" and such. In short, it is by no simple change and will affect a lot of rules... One of the reasons I would like to simplify the compiler and let it accept more code, which could be wrong, and filter it after parsing... but well... time and money speak against it atm.
bye blackdrag
----------------------------------------------------------------------
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Re: Command Chain in assert
Posted by Jochen Theodorou <bl...@gmx.org>.
On 09.11.2015 14:29, Winnebeck, Jason wrote:
> That ticket was useful. Just out of curiosity, is there a way to make
> the DSL work if I do provide a function assert? I’m not sure it could,
> because you’d need to support operators, and also when I tried to make
> such a DSL I was not able to actually declare any symbol assert and be
> able to call it how I’d expect. Even if it worked you’d lose power
> assert. I wonder (not that I think it would be worth it) if it’s even
> possible to implement with an AST? I’m thinking even that is not
> possible because Groovy can’t even parse the syntax so you’d never get
> to AST stage.
transforms still require that the program can be parsed... so no, it
would not work with them
as for the problem itself... let me try making an example...
assert foo x == bar y
you interpret that as
assert foo(x) == bar(y)
but the compiler can interpret that as
assert foo(x==bar).y
In short the grammar cannot easily know which of those two is the right
thing, especially since both variants are valid.
We actually had maybe a similar problem with handling of = in asserts.
As you may know doing something like "assert x=1" will not be accepted
by the compiler. To solve this we basically changed the rule in the
grammar from
"assert" expression
to
"assert" assignmentLessExpression
with the later one being a sub rule that contains any expression minus
assignment. So to solve the issue in a similar way we would need
something like this:
"assert" assignmentAndEqualsLessExpression ( "==" expression)?
where assignmentAndEqualsLessExpression does, in a similar matter, no
allow for expressions with directly a == in it.
And now the big trouble.... the command chain rules are not of that
kind. They allow "==" and such. In short, it is by no simple change and
will affect a lot of rules... One of the reasons I would like to
simplify the compiler and let it accept more code, which could be wrong,
and filter it after parsing... but well... time and money speak against
it atm.
bye blackdrag
RE: Command Chain in assert
Posted by "Winnebeck, Jason" <Ja...@windstream.com>.
That ticket was useful. Just out of curiosity, is there a way to make the DSL work if I do provide a function assert? I’m not sure it could, because you’d need to support operators, and also when I tried to make such a DSL I was not able to actually declare any symbol assert and be able to call it how I’d expect. Even if it worked you’d lose power assert. I wonder (not that I think it would be worth it) if it’s even possible to implement with an AST? I’m thinking even that is not possible because Groovy can’t even parse the syntax so you’d never get to AST stage.
Jason
From: Paul King [mailto:paulk@asert.com.au]
Sent: Sunday, November 08, 2015 1:27 AM
To: users@groovy.incubator.apache.org
Subject: Re: Command Chain in assert
To rephrase slightly, it's not *currently* possible. We could change the grammar and add a special parsing rule but then that would probably rule out DSLs with assert as the first word. The parens proposal in the previously referenced jira is more likely the way we'd want to go.
On 8 Nov 2015 3:17 am, "Pascal Schumacher" <pa...@gmx.net>> wrote:
I guess it's not possible. :(
There is already an enhancement request https://issues.apache.org/jira/browse/GROOVY-4808 "Command Chain + Power Assert doesn't work" in JIRA.
-Pascal
Am 06.11.2015 um 22:42 schrieb Winnebeck, Jason:
Is it possible to support command chain in asserts? I'm trying to create a testing DSL.
The expression item("abc").exists will return a boolean. So I can do this:
item "abc" exists
But I can't do this:
assert item "abc" exists
Is something like that possible?
Jason
----------------------------------------------------------------------
This email message and any attachments are for the sole use of the intended recipient(s). Any unauthorized review, use, disclosure or distribution is prohibited. If you are not the intended recipient, please contact the sender by reply email and destroy all copies of the original message and any attachments.
Re: Command Chain in assert
Posted by Paul King <pa...@asert.com.au>.
To rephrase slightly, it's not *currently* possible. We could change the
grammar and add a special parsing rule but then that would probably rule
out DSLs with assert as the first word. The parens proposal in the
previously referenced jira is more likely the way we'd want to go.
On 8 Nov 2015 3:17 am, "Pascal Schumacher" <pa...@gmx.net> wrote:
> I guess it's not possible. :(
>
> There is already an enhancement request
> https://issues.apache.org/jira/browse/GROOVY-4808 "Command Chain + Power
> Assert doesn't work" in JIRA.
>
> -Pascal
>
> Am 06.11.2015 um 22:42 schrieb Winnebeck, Jason:
>
>> Is it possible to support command chain in asserts? I'm trying to create
>> a testing DSL.
>>
>> The expression item("abc").exists will return a boolean. So I can do this:
>>
>> item "abc" exists
>>
>> But I can't do this:
>> assert item "abc" exists
>>
>> Is something like that possible?
>>
>> Jason
>>
>> ----------------------------------------------------------------------
>> This email message and any attachments are for the sole use of the
>> intended recipient(s). Any unauthorized review, use, disclosure or
>> distribution is prohibited. If you are not the intended recipient, please
>> contact the sender by reply email and destroy all copies of the original
>> message and any attachments.
>>
>
>
Re: Command Chain in assert
Posted by Pascal Schumacher <pa...@gmx.net>.
I guess it's not possible. :(
There is already an enhancement request
https://issues.apache.org/jira/browse/GROOVY-4808 "Command Chain + Power
Assert doesn't work" in JIRA.
-Pascal
Am 06.11.2015 um 22:42 schrieb Winnebeck, Jason:
> Is it possible to support command chain in asserts? I'm trying to create a testing DSL.
>
> The expression item("abc").exists will return a boolean. So I can do this:
>
> item "abc" exists
>
> But I can't do this:
> assert item "abc" exists
>
> Is something like that possible?
>
> Jason
>
> ----------------------------------------------------------------------
> This email message and any attachments are for the sole use of the intended recipient(s). Any unauthorized review, use, disclosure or distribution is prohibited. If you are not the intended recipient, please contact the sender by reply email and destroy all copies of the original message and any attachments.